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January 3, 2007, HiRISE release
djellison
post Jan 4 2007, 12:06 AM
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http://hiroc.lpl.arizona.edu/images/PSP/release_007.html

No Ares Vallis yet (booooooo) smile.gif

Lots of more varied northern plains in this one.

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Stu
post Jan 4 2007, 12:20 AM
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QUOTE (djellison @ Jan 4 2007, 12:06 AM) *
Lots of more varied northern plains in this one.


Yep... here's one that looks like a close-up of sandpaper... (click) ooh, here's one that looks more like glass paper, a bit rougher... (click) ah, now this one looks is grainy black and white, while (click) this one looks like grainy white and black... wink.gif

Only joking... all valuable stuff, I know, but come on, "my" crater in Ganges is just over there guys, screaming at you to take its picture... tongue.gif


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babakm
post Jan 4 2007, 02:53 PM
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The last Northern Plains image (PSP_001497_2480) has another high-albedo crater floor in its lower right corner.

Does anyone remember a remotely "fresh" impact crater in any of the Northern Plains images? I understand the area we've looked at is minuscule, but if none appear, one has too look at serious surface compositional differences (very shallow ice? dust-covered permafrost?) as possible explanations.
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nprev
post Jan 5 2007, 02:44 AM
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That particular crater doesn't look fresh in comparison to others in the region, but it is indeed deeper than them. Looks like a (seasonal?) deposit of frost/ice has accumulated within, assuming that the prevailing wind direction is from the lower-left of the image.


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MarsIsImportant
post Jan 6 2007, 03:23 PM
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The most interesting image for this release is this:

http://hiroc.lpl.arizona.edu/images/PSP/PSP_001482_2065/

A close look reveals a series of scattered craters along ancient small channels. Since the conglomeration of craters is on ground that seems younger than the surrounding area, this suggests that many of these small craters could actually be SINK holes.
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Bob Shaw
post Jan 6 2007, 04:06 PM
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QUOTE (MarsIsImportant @ Jan 6 2007, 03:23 PM) *
A close look reveals a series of scattered craters along ancient small channels. Since the conglomeration of craters is on ground that seems younger than the surrounding area, this suggests that many of these small craters could actually be SINK holes.



Interesting - can you crop them out, please? I see a dust free (ish) landscape at the top, lava-filled valleys with very old crater hills bounding them in the middle, and a dusty landscape at the bottom.

The attached image shows, at the top, the old hills, with the clearly defined edges of the lava flows, and in the centre, a pre-existing channel which has been filled by lava.

Attached Image



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MarsIsImportant
post Jan 7 2007, 04:26 AM
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Attached Image
Here are a few of the many that are all over the place. They tend to link some of the craters together. Note also that these channels cuts across both old and new terrain, as you identified.
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MarsIsImportant
post Jan 7 2007, 05:17 AM
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Here's a link to a color Mar's Express Image of the same area. The caption clearly says water related, presumed to be from glacial reservoirs.

http://www.esa.int/SPECIALS/Mars_Express/SEMMBP1PGQD_1.html
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Bob Shaw
post Jan 7 2007, 01:38 PM
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QUOTE (MarsIsImportant @ Jan 7 2007, 04:26 AM) *
Here are a few of the many that are all over the place. They tend to link some of the craters together. Note also that these channels cuts across both old and new terrain, as you identified.


It's a helluva thing when two people see such different things! I see a few semi-submerged channels in the 'new' terrain, and a heavily-cratered 'old' surface (in quotes because both are hardly young!). The linear features, where I see them at all, seem simply like random cratering (and where there are twin craters and the like, then I just see groups of secondaries on that ancient surface). The channels are part of the older terrain, and simply get filled by the new material, which is only a few tens of feet thick and sometimes gives a hint of the landforms below it - hence the channels which appear in the new areas.

It all looks so much more like lava to me than water-based morphologies - for example, look at the boundary in the top left corner where you can see layers, like one lava flow on top of another. At the 'shore' there are two distinct lobate fronts, too.

As I said, we're both looking and seeing quite dissimilar histories! Ah, the joy!



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Bob Shaw
post Jan 7 2007, 01:43 PM
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QUOTE (MarsIsImportant @ Jan 7 2007, 05:17 AM) *
Here's a link to a color Mar's Express Image of the same area. The caption clearly says water related, presumed to be from glacial reservoirs.



I realise they have their own spacecraft and all that, and lots of guys interpreting the images, but I have to confess that I rarely take ESA captions as being 100% reliable. They're overly keen on dramatic interpretations in my view, although I agree that Kasei Vallis is commonly accepted as having a watery history.


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MarsIsImportant
post Jan 8 2007, 05:50 AM
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The problem with a lava interpretation is that such a flow would either completely destroy or cover up any hint of such channels, unless they were extraordinarily deep. The scale of these larger flows suggests any such lava formed feature here should be quite thick. Plus the craters are not anything close to random in my opinion. I see clear dentritic patterns here, with many craters or former craters along the paths. You may only see a few semi-submerged channels in the 'new' terrain (new and old are relative terms here), but I see many. The fact that they can be seen is exactly the whole point. We should not be able to see them at all, if this is purely a lava feature. Crater numbers under these circumstance cannot be relied upon to establish relative age--layering is more important.

Old craters should have shallow slopes. Many near the area that I drew the red lines do not. In fact, many of the slopes appear to be practically vertical. Lava flows can form similar structures, but the flows themselves would destroy our ability to observe any remaining underlying structures from satellite view. Also, many of the these small channels traverse across and sometimes almost perpendicular to the more apparent larger flow, the one that you suggest is from lava.

When there is plenty of evidence for water involvement in the creation of other regional structures, we need to consider how much water played a role here too. Catastrophic flooding can create depositional signatures that allow us to observe underlying features fairly easily. If groundwater continued to flow underneath, it would possibly undercut layered structures above given enough time. Karst landscapes can occur under a number of different scenarios. In fact, this could happen even if these larger flows are lava relics.

Regardless of interpretation, I merely point out that these are the most interesting images of the bunch from January 3rd. They deserve closer inspection and a more thorough analysis. Unfortunately for me, the file is too big--until I upgrade my computer. If water played a role, it does not mean that this is necessarily recent activity. They could be as much as a billion years old. But if they are that old, how did many of these craters remain such sharp features?
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CosmicRocker
post Jan 9 2007, 06:23 AM
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QUOTE (MarsIsImportant @ Jan 6 2007, 09:23 AM) *
The most interesting image for this release is this:
http://hiroc.lpl.arizona.edu/images/PSP/PSP_001482_2065/ ...
I independently decided it was the most interesting image of the bunch and downloaded it today. Tonight, I realized it was the same one you people were talking about. Every time I download one of these I run into the same problem; I get lost in the image and don't get around to posting a crop. I hope to correct that tonight.

This is some of the strangest Martian terrain I've seen yet. An anomalous concentration of scalloped craters are visible here. A fair number of them display bright rays. What's up with that? You'll need to see the full sized version to realize how common such craters are here, but I am posting a crop containing two representative craters at full scale. (25cm/pixel)

I also have a question for a HiRise person, or anyone else who cares to comment. This jp2 displays as a rectilinear grid of dots over most of the area. The entire right side of the full swath seems to be at a lower resolution than the left side. (The lower res part is not visible in the crop I am posting, but the rectilinear grid of dots is.) What's up with that?

Attached Image


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Bob Shaw
post Jan 9 2007, 08:42 AM
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QUOTE (CosmicRocker @ Jan 9 2007, 06:23 AM) *
This is some of the strangest Martian terrain I've seen yet. An anomalous concentration of scalloped craters are visible here. A fair number of them display bright rays. What's up with that? You'll need to see the full sized version to realize how common such craters are here, but I am posting a crop containing two representative craters at full scale. (25cm/pixel)


Hmmm... ...those are seriously rotten craters! They're like Victoria, but as the newer one still has it's debris field then it's obviously a somewhat different story. Having said that, the degree of decay in the walls really does suggest a high sub-surface water content after all...


Bob Shaw


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tuvas
post Jan 9 2007, 02:52 PM
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QUOTE (CosmicRocker @ Jan 8 2007, 11:23 PM) *
I also have a question for a HiRise person, or anyone else who cares to comment. This jp2 displays as a rectilinear grid of dots over most of the area. The entire right side of the full swath seems to be at a lower resolution than the left side. (The lower res part is not visible in the crop I am posting, but the rectilinear grid of dots is.) What's up with that?

Attached Image


Lots of the HiRISE images are taken in a mode we refer to as "Boresight". Remember that HiRISE has 14 CCDs, 10 RED and 4 color, two each of IR and Blue-green. Boresight works roughly by taking a bin 2 or 4 image for the outside part of the image, and taking bin 1 for the red part of the center, and taking bin 2 or 4 for the color strip. This is done to save bandwidth frequently. So, you aren't just imagining it, it is real. Hope this helps!
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ugordan
post Jan 9 2007, 03:18 PM
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But what's with the graininess in this image? It doesn't look like binning, it looks like ...well, grains? It looks like the effect of a very low S/N ratio.


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